Future HEP Research Articles

The [formula omitted]-RWELL for future HEP challenges

The challenges posed by the forthcoming High-Energy Physics experiments require advanced particle detection technologies that are industrially scalable. The μ-RWELL, a single-amplification stage resistive MPGD utilizing sequential build-up (SBU) technology, addresses these needs. This paper reviews the main characteristics of the detector, the design of high-rate layouts, and their testing at INFN-LNF. It provides a detailed description of the detector construction processes at ELTOS and the CERN MPT Workshop. The findings highlight the industrial feasibility of detector construction, offering benefits in production time and cost. A significant focus is on the production of large DLC foils, which are essential for the detector’s amplification stage. This was facilitated by the acquisition of a DC-magnetron sputtering machine through a CERN-INFN collaboration. Detailed test results using an X-ray gun at LNF and particle beams at the CERN North Area clearly show that the detector achieves a gas gain of 104 and a rate capability greater than 1 MHz/cm2, while the efficiency of the optimized high-rate layout is about 98%. Preliminary outcomes from the 2023 co-production pilot test show a production yield larger than 90%. This successful technology transfer marks a step towards building larger detectors for future HEP challenges.

Detector-embedded reconstruction of complex primitives using FPGAs

The slowdown of Moore’s law and the growing requirements of future HEP experiments with ever-increasing data rates pose important computational challenges for data reconstruction and trigger systems, encouraging the exploration of new computing methodologies. In this work we discuss a FPGA-based tracking system, relying on a massively parallel pattern recognition approach, inspired by the processing of visual images by the natural brain (“retina architecture”). This method allows a large efficiency of utilisation of the hardware, low power consumption and very low latencies. Based on this approach, a device has been designed within the LHCb Upgrade-II project, with the goal of performing track reconstruction in the forward acceptance region in real-time during the upcoming Run 4 of the LHC. This innovative device will perform track reconstruction before the event-building, in a short enough time to provide pre-reconstructed tracks (“primitives”) transparently to the processor farm, as if they had been generated directly by the detector. This allows significant savings in higher-level computing resources, enabling handling higher luminosities than otherwise possible. The feasibility of the project is backed up by the results of tests performed on a realistic hardware prototype, that has been opportunistically processing actual LHCb data in parallel with the regular DAQ in the LHC Run 3.

Silicon photomultipliers for future HEP experiments

For the particle identification systems of the future high-energy physics detectors, single-photon sensors with sub-mm granularity, high sensitivity, and mitigation strategy for operation in the neutron-irradiated areas are needed. Silicon photomultipliers are considered a baseline technology because of their high photon detection efficiency, good timing resolution, and low operating voltage compared to those of vacuum-based photo sensors. After neutron irradiation, the dark counts increase dramatically and distort the signal baseline, making the single photons indistinguishable. Although the DCR of different unirradiated SiPMs varies, the devices show very similar rates when irradiated to high doses. In this work, we investigated the performance parameters of FBK NUV-HD-RH UHD-DE 1 mm2 devices and determined the working temperature. We show that the maximum operation temperature for samples irradiated with a fluence of 1012 neq/cm2 is around -100°C.

Performance of thin-RPC detectors for high rate applications with eco-friendly gas mixtures

In the last few years, an intense R &D activity on particle detectors for future HEP applications has been carried on with the aim of developing new techniques as well as studying the performance of already existing detectors when operated in a high rate environment. As for Resistive Plate Chamber detectors, the main challenges to face are the improvement of their detection capabilities and longevity at very high-rates, and the search for new eco-friendly gasmixtures free from greenhouse components. Results obtained in the framework of the RPC ECOGas@GIF++ Collaboration on a thin-Resistive Plate Chamber exposed at the CERN Gamma Irradiation Facility and operated with eco-friendly gas mixtures based on Tetrafluoropropene and Carbon dioxide will be discussed in this paper.

Eco-friendly Resistive Plate Chambers for detectors in future HEP applications

Resistive Plate Chamber detectors are largely used in current High Energy Physics experiments, typically operated in avalanche mode with large fractions of Tetrafluoroethane (C2H2F4), a gas recently banned by the European Union due to its high Global Warming Potential (GWP). An intense R&D activity is ongoing to improve RPC technology in view of future HEP applications. In the last few years the RPC EcoGas@GIF++ Collaboration has been putting in place a joint effort between the ALICE, ATLAS, CMS, LHCb/SHiP and EP-DT Communities to investigate the performance of present and future RPC generations with eco-friendly gas mixtures. Detectors with different layout and electronics have been operated with ecological gas mixtures, with and without irradiation at the CERN Gamma Irradiation Facility (GIF++). Results of these performance studies together with plans for an aging test campaign are discussed in this article.

Fast and Radiation Hard Inorganic Scintillators for Future HEP Experiments

Future HEP experiments at the energy and intensity frontiers require fast and ultrafast inorganic scintillators with excellent radiation hardness to face the challenges of unprecedented event rate and severe radiation environment. We report recent progress in fast and ultrafast inorganic scintillators for future HEP experiments. Examples are LYSO crystals and LuAG ceramics for an ultra-compact shashlik sampling calorimeter for the HL-LHC and the proposed FCC-hh, and yttrium doped BaF2 crystals for the proposed Mu2e-II experiment. Applications for GHz hard X-ray imaging will also be discussed.

Key4hep, a framework for future HEP experiments and its use in FCC

The road map to the FCC Feasibility Study Report, for submission to the next Update of the European Strategy for Particle Physics, will require detailed simulation and advanced reconstruction algorithms to explore and maximise the physics reach of proposed detector solutions. The optimisation process will require maximal flexibility in changing detector geometries, materials and sensitive areas, and efficient tools to quantify the overall performance. To synergise such developments, the CEPC, CLIC, FCC, ILC and SCT communities have engaged in the commissioning of a ‘Turnkey Software Stack’ (Key4hep), which would provide all the necessary ingredients, from simulation to analysis, for future experiments. This approach is based on the positive experience of the linear collider projects ILC and CLIC, which have developed and used a common software stack (iLCSoft) over the last decade. Key4hep aims to cover most, if not all, future linear and circular machines colliding leptons (electrons, muons) and hadrons. The common software ecosystem will facilitate writing specific components for experiments ensuring coherency and maximising the re-use of established solutions. Project-specific software frameworks will require adaptation to fully profit from the common software base. In this essay, we present the status and plans for re-framing the FCC software framework, FCCSW, around Key4hep and discuss the challenges associated with the transition.

Performance of a geometric deep learning pipeline for HL-LHC particle tracking

The Exa.TrkX project has applied geometric learning concepts such as metric learning and graph neural networks to HEP particle tracking. Exa.TrkX’s tracking pipeline groups detector measurements to form track candidates and filters them. The pipeline, originally developed using the TrackML dataset (a simulation of an LHC-inspired tracking detector), has been demonstrated on other detectors, including DUNE Liquid Argon TPC and CMS High-Granularity Calorimeter. This paper documents new developments needed to study the physics and computing performance of the Exa.TrkX pipeline on the full TrackML dataset, a first step towards validating the pipeline using ATLAS and CMS data. The pipeline achieves tracking efficiency and purity similar to production tracking algorithms. Crucially for future HEP applications, the pipeline benefits significantly from GPU acceleration, and its computational requirements scale close to linearly with the number of particles in the event.

Towards a Turnkey Software Stack for HEP Experiments

Future HEP experiments require detailed simulation and advanced reconstruction algorithms to explore the physics reach of their proposed machines and to design, optimise, and study the detector geometry and performance. To synergize the development of the CLIC and FCC software efforts, the CERN EP R&D roadmap proposes the creation of a “Turnkey Software Stack”, which is foreseen to provide all the necessary ingredients, from simulation to analysis, for future experiments; not only CLIC and FCC, but also for proposed Super-tau-charm factories, CEPC, and ILC. The software stack will facilitate writing specific software for experiments ensuring coherency and maximising the re-use of established packages to benefit from existing solutions and community developments, for example, ROOT, Geant4, DD4hep, Gaudi and podio. As a showcase for the software stack, the existing CLIC reconstruction software, written for iLCSoft, is being to be ported to Gaudi. In parallel, the back-end of the LCIO event data model can be replaced by an implementation in podio. These changes will enable the sharing of the algorithms with other users of the software stack. We will present the current status and plans of the turnkey software stack, with a focus of the adaptation of the CLIC reconstruction chain to Gaudi and podio, and detail the plans for future developments to generalise their applicability to FCC and beyond.

PICOSEC-Micromegas: Robustness measurements and study of different photocathode materials

Detectors with a time resolution of 20-30 ps and a reliable performance in high particles flux environments are necessary for an accurate vertex separation in future HEP experiments. The PICOSEC-Micromegas detector concept is a Micro-Pattern Gaseous Detector (MPGD) based solution addressing this particular challenge. The PICOSEC-Micromegas concept is based on a Micromegas detector coupled to a Cherenkov radiator and a photocathode. In this detector concept, all primary electrons are initiated in the photocathode and the time jitter fluctuations are reduced. Different resistive anode layers have been tested with the goal of preserving a stable detector operation in a high intensity pion beam. One important characteristic of a gaseous detector in a high flux environment is the ion backflow (IBF). That can cause damage to more fragile photocathode materials like CsI. Various types of photocathode materials have been tested in order to find a robust solution against IBF bombardment.

Development of Yttrium-Doped BaF2 Crystals for Future HEP Experiments

Because of their ultrafast scintillation with subnanosecond decay time, barium fluoride (BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) crystals have attracted broad interest in the high energy physics and nuclear physics communities. One crucial issue, however, is its slow scintillation component with 600-ns decay time, which causes pile-up in a high rate environment. Previous studies show that the slow component can be suppressed effectively by rare earth doping. In this paper, we report investigations on a set of Φ 18 × 21 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> cylinders doped with different yttrium levels grown at Beijing Glass Research Institute (BGRI), from which the optimized yttrium doping level was determined. A Φ 40 × 160 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ingot with 5 atomic % (at.%) yttrium doping was consequently grown at BGRI and was used to cut one 25 × 25 × 100 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> crystal and several thin slices. Their optical and scintillation properties were measured at Caltech. The results show that yttrium doping effectively suppresses the slow component while maintaining its ultrafast light unchanged. Research and development will continue to develop large-size BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :Y crystals with improved optical quality for a fast BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :Y crystal calorimeter for Mu2e-II.

La- and La-/Ce-Doped BaF2 Crystals for Future HEP Experiments at the Energy and Intensity Frontiers Part I

In addition to La-doped barium fluoride (BaF2) crystals, La/Ce co-doped BaF2 crystals were also investigated at the California Institute of Technology, Pasadena, CA, USA. Strong cerium-induced emissions peaked at 305 and 320 nm with a decay time of 25 ns were observed, in addition to the fast and slow scintillation at 220 and 300 nm, respectively. The La/Ce co-doping was also found effective in suppressing the slow component in BaF2. Compared to La-doped crystals, the La/Ce co-doped crystals have a better light output in both 50- and 2500-ns gate. The fast/slow ratio of La/Ce co-doped crystal was found to be about 1/1, similar to La-doping, which is also considered not sufficient for pile-up suppression. A 20-cm-long La/Ce co-doped BaF2 crystal shows also excellent optical quality and light response uniformity.

La- and La-/Ce-Doped BaF2 Crystals for Future HEP Experiments at the Energy and Intensity Frontiers Part II

In addition to La-doped barium fluoride (BaF2) crystals, La/Ce co-doped BaF2 crystals were also investigated at the California Institute of Technology, Pasadena, CA, USA. Strong cerium-induced emissions peaked at 305 and 320 nm with a decay time of 25 ns were observed, in addition to the fast and slow scintillation at 220 and 300 nm, respectively. The La/Ce co-doping was also found effective in suppressing the slow component in BaF2. Compared to La-doped crystals, the La/Ce co-doped crystals have a better light output in both 50- and 2500-ns gate. The fast/slow ratio of La/Ce co-doped crystal was found to be about 1/1, similar to La-doping, which is also considered not sufficient for pile-up suppression. A 20-cm-long La/Ce co-doped BaF2 crystal shows also excellent optical quality and light response uniformity.

Neutron-Induced Radiation Damage in BaF2, LYSO/LFS and PWO Crystals

One crucial issue for applications of inorganic scintillators in future HEP experiments is radiation damage in a severe radiation environment, such as the HL-LHC. While radiation damage induced by ionization dose is well understood, investigations are on-going to understand radiation damage induced by hadrons, including both charged hadrons and neutrons. Aiming at understanding neutron induced radiation damage in fast inorganic scintillators, BaF2, LYSO/LFS and PWO crystals were irradiated at LANSCE by a combination of particles, including neutrons, protons and γ-rays. The results indicate that LYSO/LFS and BaF2 crystal plates are radiation hard up to 4 × 1015 fast neutrons/cm2.

A Parallelised ROOT for Future HEP Data Processing

In the coming years, HEP data processing will need to exploit parallelism on present and future hardware resources to sustain the bandwidth requirements. As one of the cornerstones of the HEP software ecosystem, ROOT embraced an ambitious parallelisation plan which delivered compelling results. In this contribution the strategy is characterised as well as its evolution in the medium term. The units of the ROOT framework are discussed where task and data parallelism have been introduced, with runtime and scaling measurements. We will give an overview of concurrent operations in ROOT, for instance in the areas of I/O (reading and writing of data), fitting / minimization, and data analysis. This paper introduces the programming model and use cases for explicit and implicit parallelism, where the former is explicit in user code and the latter is implicitly managed by ROOT internally.

Ultrafast and Radiation Hard Inorganic Scintillators for Future HEP Experiments

Future HEP experiments at the energy and intensity frontiers require fast and ultrafast inorganic scintillators with excellent radiation hardness to face the challenges of unprecedented event rate and severe radiation environment. This paper reports recent progresses in fast and ultrafast inorganic scintillators, such as LYSO:Ce crystals and LuAG:Ce ceramics for an inorganic scintillator based shashlik sampling calorimeter and yttrium doped BaF2 crystals for the proposed Mu2e-II experiment. Applications of ultrafast inorganic scintillators in Gigahertz hard X-ray imaging will also be discussed.

Performance of a high-throughput tracking processor implemented on Stratix-V FPGA

Abstract Two of the biggest challenges for future HEP experiments at hadron colliders are triggering and track reconstruction of high-multiplicity events, where collisions have multiple primary vertices. The highly-non-linear scaling of computing power required for these tasks encourages the adoption of non-traditional, specialized architectures. Amongst them, the “artificial retina” approach, inspired by the architecture of the vision system in the living brain, promises large efficiency of hardware utilization, low-power and low-latency when implemented in state-of-art FPGA devices. The INFN-RETINA project has been a 3-year effort dedicated to investigate the potential of that approach in a real-time tracking processor at Level-0 of the LHC HEP experiments. We present results from studies performed on a prototype system capable of carrying out track reconstruction in a generic 6-layer silicon-strip detector with sub- μ s latency at an event rate in excess of 30 MHz, and how a large-scale system can be implemented on multiple boards interconnected with high-speed optical links. Possible applications to real experimental environments will be also discussed.

The next generation of crystal detectors

Crystal detectors have been used widely in high energy and nuclear physics experiments, medical instruments and homeland security applications. Novel crystal detectors are continuously being discovered and developed in academia and in industry. In high energy and nuclear physics experiments, total absorption electromagnetic calorimeters (ECAL) made of inorganic crystals are known for their superb energy resolution and detection efficiency for photon and electron measurements [1]. A crystal ECAL is thus the choice for those experiments where precision measurements of photons and electrons are crucial for their physics missions. Examples are the Crystal Ball NaI(Tl) ECAL, the L3 BGO ECAL and the BaBar CsI(Tl) ECAL in lepton colliders, the kTeV CsI ECAL and the CMS PWO ECAL in hadron colliders and the Fermi CsI(Tl) ECAL in space. For future HEP experiments at the energy and intensity frontiers, however, the crystal detectors used in the above mentioned ECALs are either not bright and fast enough, or not radiation hard enough. Crystal detectors have also been proposed to build a Homogeneous Hadron Calorimeter (HHCAL) to achieve unprecedented jet mass resolution by duel readout of both Cherenkov and scintillation light [2], where development of cost-effective crystal detectors is a crucial issue because of the huge crystal volume required [3]. This contribution discusses several R&D directions for the next generation of crystal detectors for future HEP experiments.

A Very Compact Crystal Shashlik Electromagnetic Calorimeter for Future HEP Experiments

A very compact crystal based shashlik calorimeter is proposed for future HEP experiments in an extreme harsh radiation environment, such as the proposed HL-LHC. Thin crystal plates are used as the sensitive medium to reduce the light path length and thus the radiation damage effects and the calorimeter cost. A design of such a calorimeter uses tungsten as absorber, LYSO crystals as active medium, and liquid scintillator filled quartz capillaries as WLS to transport scintillating light to photodetectors. Initial calorimeter design and performance of prototype modules are presented. Possible optimizations are discussed.

Total Ionizing Dose effects on a 28 nm Hi-K metal-gate CMOS technology up to 1 Grad

This paper presents the results of an irradiation study on single transistors manufactured in a 28 nm high-k commercial CMOS technology up to 1 Grad. Both nMOSFET and pMOSFET transistors have been irradiated and electrical parameters have been measured. For nMOSFETs, the leakage current shows an increase of 2–3 orders of magnitude, while only moderate degradation for other parameters has been observed. For pMOSFETs, a more severe degradation of parameters has been measured, especially in the drain current. This work is relevant as the evaluation of a new generation of CMOS technologies to be used in future HEP experiments.